1. Field of the Invention
The present invention relates to a multiple sheets feeding detection apparatus, a sorter, and a method of detecting multiple sheets feeding, and more particularly, to those multiple sheets feeding detection apparatus, sorter, and method of detecting multiple sheets feeding for use to detect feeding of multiple objects which are target subject of detection (referred to simply as a target object, appropriately) and each of which has an RFID (Radio Frequency Identification) tag attached thereto, and to remove target objects involved in multiple sheets feeding.
2. Description of the Prior Art
Conventional multiple sheets feeding detection apparatuses provided in a sorter for paper sheets and the like incorporate a shifting mechanism or a separating mechanism to detect multiple sheets feeding in a condition where those paper sheets are forcibly bent.
As a multiple sheets feeding detection apparatus incorporating the shifting mechanism, disclosed is for example the technology of a double sheet feeding detection apparatus that measures the length of paper sheets before and after they pass through the sifting mechanism and detects double sheet feeding on the basis of the measurement result (see Patent Document 1).
Furthermore, as a multiple sheets feeding detection apparatus incorporating the separating mechanism, disclosed is for example the technology of a double sheet feeding detection apparatus for paper sheets that uses two belts, light emitters, and light receivers to detect double sheet feeding for paper sheets (see Patent Documents 1 and 2).
A conventional sorter (transporter) 100 comprises, as shown in FIGS. 9A and 9B, a guide rail 150 formed into an endless loop, a plurality of carrier boxes 120 that travel along the circular guide rail 150, a feeder 112 that feeds target objects 103 to be sorted, a drop portion 113 that drops the target object 103 into the carrier box 120, and carrier portion 114 for carrying the target object 103 from the feeder 112 to the drop portion 113. This sorter 100 can sort the target object 103 dropped in the carrier box 120 into a predetermined gathering portion 110 (see Patent Document 3).
This sorter 100 is configured so that the bottom cover (not shown) of the carrier box 120 is opened above the predetermined gathering portion 110 and then the dropped target object 103 is dropped from the carrier box 120 into the predetermined gathering portion 110.
When the target object 103 is a paper sheet, the thickness and frictional coefficient of the paper sheet, the surface condition influenced by humidity, or the attraction property of static electricity make two or more paper sheets stick together just like a single sheet of paper. At this time, multiple sheets feeding occurs, and the paper sheet sticking to the underside of another is sorted to a wrong gathering portion 110. That is, paper sheets fed must be carried one by one, and the target object 103 to be sorted has to solely be carried by each carrier box 120.
In order to eliminate this inconvenience, the sorter 100 is provided with the foregoing double sheet feeding detection apparatus for paper sheets (not shown in FIGS. 9A and 9B) in the drop portion 113 or in the vicinity thereof. By using this double sheet feeding detection apparatus of the sorter 100, one paper sheet is dropped always one by one in each carrier box 120.
By the way, recent article sorting devices automatically sort articles by reading information from barcodes or radio frequency ID (identification) tags attached to the outside of those articles. This technique has been studied actively as a product identification and management technology in place of barcodes.
For example, the technology of an article sorting apparatus which uses multiread-based radio frequency ID tags is disclosed. In this technology, a multiread-based radio frequency ID tag is attached to all articles grouped into bundles, and the article sorting apparatus has sorting destination determination portion for comparing sorting information among articles included in one grouped bundle, and determining to sort the articles in the one grouped bundle to the same sorting destination when sorting destinations of those articles in the one grouped bundle are the same (see Patent Document 4).
According to this technology, even in the case of handling a plurality of articles as a bundle, the workability is enhanced because articles are sorted to appropriate sorting chutes.
Furthermore, the technology of a transport system is disclosed, in which transport information is written to radio frequency tags each provided with an IC memory, and the radio frequency tags are attached to transport items so that these transport items are transported in accordance with transport information obtained from their respective radio frequency tags attached (see Patent Document 5).
According to this technology, the transport efficiency of transport items such as parcels can be increased, and tracking and monitoring operations for those transport items can be facilitated.
Moreover, the technology of a distribution system is disclosed, in which distribution centers or retail stores use product information in barcodes or radio frequency tags written by vendors so as thereby to enhance the workability (see Patent Document 6).
According to this technology, the working efficiency of sorting or transshipping products at distribution centers and retail stores, as well as during transportation, can be improved.
Moreover, the technology of a paper sheet determination apparatus is disclosed which determines the number of paper sheets by use of a thickness sensor (see Patent Document 7).
According to this technology, even when paper sheets are overlapping or skewed and paper sheets having folded, torn, or cut portions are carried, the number or type of sheets can accurately be determined.
(Patent Document 1) Japanese Utility Model Laid-Open No. 57-011144 (claim 1, FIG. 1)
(Patent Document 2) Japanese Patent Laid-Open No. 56-161241 (claim 1, FIGS. 1 and 4)
(Patent Document 3) Japanese Patent Laid-Open No. 56-161242 (claim 1, FIGS. 1 and 4)
(Patent Document 4) Japanese Patent Laid-Open No. 2003-237926 (FIG. 7)
(Patent Document 5) Japanese Patent Laid-Open No. 2001-39533 (claim 1)
(Patent Document 6) Japanese Patent Laid-Open No. 2001-205199 (claim 1)
(Patent Document 7) Japanese Patent Laid-Open No. 2003-288628 (claim 1)
The above described sorter 100, however, cannot raise the processing capability thereof because of a bottleneck in the conventional double sheet feeding detection apparatus (see Patent Documents 2 and 3) that detects double sheet feeding in a condition where paper sheets are forcibly bent and separated from each other.
Specifically, for greater processing capability of the sorter 100, the sheet handling speed has to be increased. However, high-speed operations of the above double sheet feeding detection apparatus may cause folds or any other damages to paper sheets, so that this apparatus is disadvantageously not allowed to handle paper sheets at high speed.
Another double sheet feeding detection apparatus (see Patent Document 1) detects multiple sheets feeding by separating paper sheets through the physical shifting operation, which also causes folds or any other damages to paper sheets when this apparatus is operated at high speed. Therefore, this apparatus is not allowed to handle paper sheets at high speed.
Furthermore, the above two types of double sheet feeding detection apparatuses are not able to separate or shift paper sheets strongly sticking together due to static electricity or other causes, even when applying the separating or shifting operations to these sticking paper sheets. Therefore, erroneous detection may occur disadvantageously.
Moreover, the above two types of double sheet feeding detection apparatuses apply external loads to detection target objects, and thus cannot detect unbendable objects or objects having soft surfaces. Therefore, a limitation is imposed on the types of target objects.